Best-Fit Computing - COLUMBUS Network Adjustment Software

EGM 96 Geoidal Model

Support for EGM 96 World Wide Geoidal Model is available with COLUMBUS. Using EGM 96, you can determine the geoidal height for any position on the ground throughout the world.

EGM 96 is a geopotential model of the Earth consisting of spherical harmonic coefficients complete to degree and order 360. This model is the result of a collaboration between the National Imagery and Mapping Agency, the NASA Goddard Space Flight Center, and the Ohio State University.

The original coefficients are offered by NIMA in an ASCII (Text) file called WW15MGH.GRD. We have converted this file to a binary format to facilitate efficient programmatic access through COLUMBUS. The binary compressed file EGM96DAT.EXE (about 3000K in size) is available for downloading. This file is a self-extracting archive. Run the EGM96DAT.EXE program to extract the binary grid file WW15MGH.COL (about 4000K in size).

After extracting the file, follow the steps in your User's Manual for Geoidal Modeling in the Tools Chapter. Follow similar steps for those described for Geoid90 thru 03 models. Do not change the name of the file WW15MGH.COL. Also, be sure to set up this file in the OPTIONS | DIRECTORIES dialog box in the Geoid Modeling File field.

Network Adjustment and Coordinate Transformation
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